Project Summary. Autoimmune or chronic inflammatory diseases such as psoriasis are caused by aberrant and overactive immune responses. While immunosuppressive drugs and various biologics have been used successfully to treat these disorders, many of these drugs have notable limitations, including the need for many of them to be applied systemically, their sometimes non-selective modes of action, their adverse side effects, their limited access to the relevant sites of inflammation, and, in the case of biologics, their high costs. Research into the molecular mechanisms by which pathogens have evolved to inhibit host immune responses has advanced the idea that microbial proteins can be used to treat chronic inflammatory or autoimmune diseases; the ?Drugs from Bugs? concept. Previous collaborative work has focused on the activities of several Yersinia enterocolitica and Escherichia coli ?effector? proteins. Effector proteins are virulence factors that are injected directly into infected host cells through a bacterial type III secretion system. A detailed understanding of how these effectors suppress host immune responses by targeting and inhibiting the regulatory components of the NF-?B pathway has been achieved. NF-?B-dependent signaling leads to the induction of pro-inflammatory cytokines known to contribute to psoriasis. The proposed approach to use effectors as anti-inflammatory proteins to treat inflammatory skin diseases overcomes several significant hurdles in the field in that 1) effectors are applied directly to relevant sites of inflammation and achieve positive therapeutic outcomes in mouse models of autoimmune or chronic skin inflammation; 2) effectors are detected at the application sites, but not systemically (e.g. regional lymph nodes or serum); 3) anti-effector antibodies are not produced, even after long-term local treatment; 4) effectors penetrate human skin samples. The central hypothesis to be tested is that direct application of the recombinant effectors rNleH1 and rNleB to skin will suppress the anomalous pro-inflammatory signaling that results in the development of psoriasis. The specific aims are: 1) Quantify the cell penetration and anti-inflammatory activities of the rNleH1 and rNleB effectors fused to cell-penetrating peptides (CPPs). 2) Characterize the cell-type specificity and activity of recombinant effectors. 3) Quantify the extent to which recombinant effectors reduce psoriasis-like phenotypes in multiple mouse models of disease. 4) Quantify the extent to which recombinant effectors penetrate through thicker barriers and are efficacious in treating other inflammatory disorders. Developing bacterial effector proteins into anti-inflammatory drugs has high potential impact to future translational approaches that may be developed to treat psoriasis.